Help with young one

I have struggled with added weight since having the first of my 4 children and flucuate pretty regularly. I have no problems eating healthy or eating the right proportions but the weight just likes to stick around. My biggest worry is for my oldest daughter who is 10. According to the doctors charts she is within her weight range but she is alot larger than she should be around her midsection. I knew from the beginning that we were going to need to watch her closer due to her biological fathers side of the family being morbidly obese, so I made sure she ate very healthy as a tot. Just like me, she likes fruits and veggies, can eat the same foods as I do, but continues to get larger. We could all stand to be a little more active, I know that, but most of the difficulties are getting her to understand how to stop eating. I try to only make enough to serve the 6-7 of us, but if there are ever any leftovers she will load up her plate again. Plus I find wrappers and containers of food hidden in her room. I don't want to lock up all of our food but I don't know how to get her to stop. I want her to be healthy, and I know she gets bullied at school becasue of her weight, but she just laughs it off every time I talk to her about it. Do I just let her eat the way she is and wait for her to realize it on her own? Do I lock up all the food in the house to keep her away from it all? I have already stopped buying most junk food to make things less appealing but even healthy snacks get eaten in excess. Any positive feedback would be greatly appreciated. Please, if you want to tell me how bad of a parent I am for letting my child become overweight...keep it to yourself.